The present invention relates to a transfer apparatus for conveying a semiconductor wafer between two locations and, more particularly, to such a transfer apparatus which can conveniently transfer such a semiconductor wafer between two locations having differing pressures without substantially affecting or disturbing the pressure at either of the two locations.
The etching of semiconductor wafer materials utilizing a gas plasma reaction in an evacuated or vacuum chamber is generally well-known in the art. The apparatus for the treatment of semiconductor wafers by such a gas plasma reaction can be classified into two major types; (1) batch, in which a plurality of sheets of wafers are placed inside of a reaction or treatment chamber for simultaneous treatment; and (2) continuous, in which the semiconductor wafers are continuously serially introduced into the reaction or treatment chamber one at a time and are individually removed from the treatment chamber after the gas plasma treatment.
Numerous prior art devices and methods have been employed for transferring the semiconductor wafers into or out of a reaction chamber for continuous treatment without disturbing or otherwise affecting the vacuum or pressure level within the reaction chamber. Most of the prior art devices employ a separate feeding or inlet chamber (air lock) adjacent the reaction or treatment chamber. A mechanical device is employed for transferring the wafers into the feeding or inlet chamber one at a time and, once the pressure within the feeding or inlet chamber has been adjusted to correspond to the pressure within the reaction chamber for transferring the wafers into the reaction chamber. In some of the prior art transfer devices, one or more conveyor belts are employed for the actual movement of the semiconductor wafer into and out of the feeding chamber. Other such devices employ piston actuated pusher members for moving the semiconductor wafers. Yet other prior art devices employ a complicated walking beam arrangement for moving the semi-conductor wafers.
While the prior art devices for moving a semi-conductor wafer into or out of a reaction chamber generally function satisfactorily, they are usually mechanically complex and, therefore, are expensive to purchase and operate and may require frequent service. In addition, because of the way in which the prior art devices operate, it is difficult if not impossible to ascertain the exact location of a particular wafer being transferred at any given time during the transfer cycle. As a result, sometimes wafers are damaged or destroyed by the opening or closing of a reaction chamber or feeding chamber door when a wafer is in the wrong position. This causes not only a loss of the wafer, but also possible contamination of the apparatus which must then be cleaned before any wafer processing can be resumed.
In addition to the previously described drawbacks, the prior art transfer devices do not lend themselves to the conducting of any pre-treatment or post-treatment processing of a wafer within the entry or exit chamber while it is being transferred. Pre-treatment processing such as hardening the photo resist material or desmearing the wafer to remove any accumulated oxide can be helpful in speeding up the etching process which occurs within the plasma treatment chamber and/or providing a better quality product. Post-treatment processes such as stripping the photo resist material off of the wafer can also be useful in speeding up the wafer production process.
The present invention provides a compact, mechanically simple wafer transfer apparatus which is inexpensive to produce and operate and yet provides a reliable, positive wafer transfer motion which permits the location of the wafer to be determined during the transfer process. The present invention also permits pre-treatment and post-treatment processing of the semiconductor wafer in conjunction with the wafer transfer process.